/* MN10300 Low level time management
*
* Copyright (C) 2007-2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
* - Derived from arch/i386/kernel/time.c
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/profile.h>
#include <linux/cnt32_to_63.h>
#include <asm/irq.h>
#include <asm/div64.h>
#include <asm/processor.h>
#include <asm/intctl-regs.h>
#include <asm/rtc.h>
#ifdef CONFIG_MN10300_RTC
unsigned long mn10300_ioclk; /* system I/O clock frequency */
unsigned long mn10300_iobclk; /* system I/O clock frequency */
unsigned long mn10300_tsc_per_HZ; /* number of ioclks per jiffy */
#endif /* CONFIG_MN10300_RTC */
static unsigned long mn10300_last_tsc; /* time-stamp counter at last time
* interrupt occurred */
static irqreturn_t timer_interrupt(int irq, void *dev_id);
static struct irqaction timer_irq = {
.handler = timer_interrupt,
.flags = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
.name = "timer",
};
static unsigned long sched_clock_multiplier;
/*
* scheduler clock - returns current time in nanosec units.
*/
unsigned long long sched_clock(void)
{
union {
unsigned long long ll;
unsigned l[2];
} tsc64, result;
unsigned long tsc, tmp;
unsigned product[3]; /* 96-bit intermediate value */
/* cnt32_to_63() is not safe with preemption */
preempt_disable();
/* read the TSC value
*/
tsc = 0 - get_cycles(); /* get_cycles() counts down */
/* expand to 64-bits.
* - sched_clock() must be called once a minute or better or the
* following will go horribly wrong - see cnt32_to_63()
*/
tsc64.ll = cnt32_to_63(tsc) & 0x7fffffffffffffffULL;
preempt_enable();
/* scale the 64-bit TSC value to a nanosecond value via a 96-bit
* intermediate
*/
asm("mulu %2,%0,%3,%0 \n" /* LSW * mult -> 0:%3:%0 */
"mulu %2,%1,%2,%1 \n" /* MSW * mult -> %2:%1:0 */
"add %3,%1 \n"
"addc 0,%2 \n" /* result in %2:%1:%0 */
: "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
: "0"(tsc64.l[0]), "1"(tsc64.l[1]), "2"(sched_clock_multiplier)
: "cc");
result.l[0] = product[1] << 16 | product[0] >> 16;
result.l[1] = product[2] << 16 | product[1] >> 16;
return result.ll;
}
/*
* initialise the scheduler clock
*/
static void __init mn10300_sched_clock_init(void)
{
sched_clock_multiplier =
__muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
}
/*
* advance the kernel's time keeping clocks (xtime and jiffies)
* - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
* there's a need to update
*/
static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
unsigned tsc, elapse;
write_seqlock(&xtime_lock);
while (tsc = get_cycles(),
elapse = mn10300_last_tsc - tsc, /* time elapsed since last
* tick */
elapse > MN10300_TSC_PER_HZ
) {
mn10300_last_tsc -= MN10300_TSC_PER_HZ;
/* advance the kernel's time tracking system */
profile_tick(CPU_PROFILING);
do_timer(1);
}
write_sequnlock(&xtime_lock);
update_process_times(user_mode(get_irq_regs()));
return IRQ_HANDLED;
}
/*
* initialise the various timers used by the main part of the kernel
*/
void __init time_init(void)
{
/* we need the prescalar running to be able to use IOCLK/8
* - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
* - IOCLK runs at Fosc rate (crystal speed)
*/
TMPSCNT |= TMPSCNT_ENABLE;
startup_timestamp_counter();
printk(KERN_INFO
"timestamp counter I/O clock running at %lu.%02lu"
" (calibrated against RTC)\n",
MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
mn10300_last_tsc = TMTSCBC;
/* use timer 0 & 1 cascaded to tick at as close to HZ as possible */
setup_irq(TMJCIRQ, &timer_irq);
set_intr_level(TMJCIRQ, TMJCICR_LEVEL);
startup_jiffies_counter();
#ifdef CONFIG_MN10300_WD_TIMER
/* start the watchdog timer */
watchdog_go();
#endif
mn10300_sched_clock_init();
}
